Microwave bandstop filters can be used to reflect or absorb unwanted signals in a microwave system. These unwanted signals can originate from co-site or externally generated interference as well as nonlinear components under high-power excitation in the system. For example, a traditional microwave bandstop filter can be composed of resonators coupled to a through line with quarter-wavelength admittance inverters between each resonator. This bandstop filter topology can produce a symmetric notch frequency response and meet a wide variety of practical specifications. However, when the traditional microwave bandstop filter topology is used for high-order filters, the total through-line length becomes long.
A long through-line leads to higher passband insertion loss, increased circuit size and weight, and larger dispersive effects. In addition, the through-line lengths are difficult to tune in production environments yet have appreciable effects on the frequency response of the filter. Thus, conventional bandpass filters have undesirably large passband insertion loss, size, and weight.
Features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.